The present invention relates to a duplicating method and arrangement and, more specifically, in a duplicating machine such as a milling machine wherein the direction and amplitude of deflection of a stylus is evaluated to control the motion of the template with which the stylus is in contact.
Duplicating methods are known wherein function generators are used to convert the deflection of the stylus into desired voltage signals for two mutually perpendicular axes.
The proportional-integral characteristic of the control system is the basic assumption for maintaining a constant deflection. However, at low duplicating speed the integrating portion as well as the unavoidable dead times in the control elements and/or the mechanical transfer elements, cause difficulties in the form of square wave oscillations or complete failure to determine the direction of deflection. For control techniques such as the use of a differentiating circuit, changes in the adjustment of the control system with changes in the speed, or similar measures only yield limited improvement. Further, other systems are known in which the direction of deflection of the stylus is used to determine the desired velocity values. Errors in this type of system, resulting, for example, from friction effects, are decreased by furnishing, for each axis, a desired deflection signal and comparing these desired deflection signals to the actual deflection in each direction. The velocity signal is then modified to effect a correction in the corresponding direction. However, errors due to friction and manufacturing tolerances cause difficulties in the system which result in duplicating speeds which vary with the direction of movement (i.e., the speed along the path is not constant) and further cause the system to operate improperly below a certain operating speed.